Ideal self? Me, with several billion dollars, living in a country with a really low tax rate. Not this one, that's for damned sure.

Highest self? Me, with a monster bag o'weed.

For me, it's a continually unfolding process of becoming aware of, confronting, processing, and (eventually--hopefully) shedding unskillful traits: I don't need to be upset about this, I don't need to resent so-and-so for that, I don't need to be judgmental over this, etc. The more I strip away, the freer, easier, and more me I feel.

So far, whenever something gets peeled away, there is always more to discover. I'm not concerned with whether there is an "end"; I'm content with the process.

I've posted this before on similar questions.
But it's one that I really try to live by.
I feel the best about myself when I do these things.

The self detached from people and their distractions. Only when you let go of the influences of other people can you know your true self, and from knowing that all constructive things follow.

Good question. My "highest self" would be having complete contentment in where I am in life. No "I wish," or "when this is done." Just a satisfaction of the now.

To recognize your own lies to yourself. We all have two voices and we actually talk with our selves. I recall when my other voice let me know I was not happy yet I provided rational to defend my other position which included the world around me. But the sacrifice was notable. Always striving to be true to myself brought me into spiritualism , the discovery of who I really am. That oneness includes hearing your own lie.
I recall giving a presentation and hated the company I worked for as well as the product. I stood up and just said fuck it to myself and quit on the spot. Wrong move for my family and responsibilities but I KNEW that all would be well if I was truthful with me. And of course it was all well. To detect your own myths and recognize which of the two voices is really you, that is oneness. I am science buff and that knowledge was instrumental in confirming truth.
Great question and a lot of thought.

Perfect balance between love of myself vs love of the universe.
Ideally at least continually striving for that balance..

Is that a real thing?

Ideals are unattainable, and chasing them is futile. I'm a human being, who strives to live an ethical life in the face of reality, with emotions that rage. It's the best I can do.

Just being me.

I don't have an ideal self. I have my self-image of who I am. That's pretty fictional enough. Then I guess on top of that, I create my own myth about who I am. I guess that is my "ideal" self. But how grounded it is in reality? God, I have no idea.

It isn't my ideal self that concerns me. It is more realistic assessment of who I am that concerns me. As my favorite protagonist said: "Face the fact. Then act." Facing the fact necessarily includes my honest self-assessment of what I am and what I am able to do.

And just how would one know that they had attained their "highest self"?

I try to hold myself to an ethical standard that I'll probably never fully realize, but to do no harm and to help where I reasonably can — and to be always kind to children and animals. And I strive to be thoughtful, to know and understand and not act unthinkingly. If I can achieve those things, I'll consider my life to have been a success.

Well, probably not what I am right now.

Trying to be selfless in someone’s time of need.

It's when I have no guilt and no remorse.

My ideal self is to be Chris Hemsworth but since that job is already taken by Chris Hemsworth I'm stuck being me.

Being a loving mom to many children...

My Ego Fizzled a long time ago... what's left is a work in progress and subject to modifications.

Burning a big, fat one, lol

Being present, mindful, and kind, to myself and to others. Ideally getting away from an "ideal," because life keeps changing. To quote a phrase, it's the journey as much as the destination. Maybe more so.

Ideals are aspirational, not a destination for your actual self. You strive for your ideals, you never get there. The important part is the striving.